The present invention relates to systems for automatically shutting off water supply, natural gas or other utilities in the event of unexpected leakage.
While a home-owner will typically shut off water and gas utilities in a home, cottage or ski chalet when leaving the residence unoccupied for an extended period, this will often not be done when the residence is left unoccupied for a shorter period, perhaps a weekend or even several weeks and is never done at night while the residence is occupied. However, if a water or gas leak occurs during the vacant period or overnight, considerable damage can be done, even over a very short period. Leaks might be caused by freezing or breakage of pipes, for example, or an earthquake.
Various systems have been designed to automatically shut off water or gas supplies to a household in the event of earthquakes or leakage. Some of these are triggered by the tremors of the earthquake. Others rely on sensing a flow in the water line. For example, U.S. Pat. No. 3,416,560 issued Dec. 17, 1968 to Bruno discloses a fluid leak monitoring apparatus which comprises a housing with a chamber therein divided into a small diameter intake chamber and a larger diameter outlet chamber. A piston is mounted in the larger chamber so that it faces downstream. A drop in the water pressure downstream due to a leak causes the piston to move in the downstream direction, throwing a switch which activates a shutoff valve.
U.S. Pat. No. 4,180,088 issued Dec. 25, 1979 to Mallett discloses another water shutoff system in which a fluid flow sensor causes water and gas supplies to be shut off when water flow is sensed and the circuit is set to automatic mode, but not otherwise. U.S. Pat. No. 4,249,565 issued Feb. 10, 1981 to Brust and U.S. Pat. No. 4,589,435 issued May 20, 1986 to Aldrich disclose timed water shutoff systems in which water is permitted to flow for a pre-set period of time before the shutoff valve is activated. Finally, U.S. Pat. No. 4,730,637 issued Mar. 15, 1988 to White discloses another water and gas shutoff system which uses a central processing unit to monitor data concerning fluid flow and temperature in the pipes and, based on the data, decides when to shut the supply of fluid to the system.
The above referenced devices cannot determine the status of the utility line once they have triggered. Utility line monitoring is not possible with sensing devices that return to equilibrium when flow stops whether under normal conditions or abnormal conditions such as voiding of the utility line after line failure and triggering of the line shut off valve. Such systems would have to be electrically activated in order for their sensing device to determine the presence or absence of flow. Building codes specifically prohibit such automatic resetting for the gas utility line and undesirable flooding could occur from the water line.
White addresses this problem for one type of potential failure in the water line by suggesting temperature measurement and trigger line shut off and water system draining. This differs from commercially available temperature monitoring alarm systems in as much as it allows for draining and the charging of the water line when the sensing condition has passed. Presumably if some problem has occurred such as earthquake failure or freezing due to inadequate draining caused by line vacuum and water tension that occurs when a non-vented line is drained, the White device would then function similarly to other flow sensing devices.